Cytospora canker of plane tree

Taxonomically, the fungus belongs to the Sordariomycetes class. It thrives in environments where the host tree exhibits reduced vigor, often due to environmental stress factors.

The fungus produces small, black, flask-shaped structures called pycnidia within the bark. These pycnidia are the hallmark of the disease and are responsible for the spread of conidia.

Infection typically begins when spores enter the tree through bark injuries, pruning wounds, sunscald areas, or frost cracks, allowing the mycelium to colonize the cambium.

The fungus is capable of saprophytic survival on dead wood, making it a persistent threat in landscapes where sanitation is neglected and dead branches are left on the ground.

The disease targets the plane tree genus, damaging both the bark and the underlying conductive tissues, which disrupts the tree's vital water and nutrient transport systems.

As the fungal cankers expand, they often girdle branches or even the main stem, leading to the rapid dieback of parts of the crown or the entire tree.

Severe infestations reduce the aesthetic value of the trees significantly, making them unsightly and prone to secondary infestations by wood-boring insects.

Damage is most prevalent in urban plantings where trees are subjected to high levels of abiotic stress, such as soil compaction, pollution, and inadequate irrigation.

In mature stands, the disease can weaken the structural integrity of the branches, posing a safety risk if dead limbs break and fall in public areas.

Initial symptoms include the formation of sunken, discolored patches on the bark, which may be reddish-brown or dark in color, often showing early signs of peeling.

During humid weather, the pycnidia erupt through the bark, releasing spore tendrils (cirrhi) that appear as orange or yellowish strands on the bark surface.

Under the infected bark, the tissues appear decayed, discolored, and necrotic. There is often a noticeable moisture deficit in the branches above the canker site.

Foliage on affected branches shows symptoms of decline: leaves may wilt, turn yellow, or brown prematurely while remaining attached to the twigs.

• Sunken cankers on branches and stems.
• Characteristic orange or yellow spore tendrils.
• Peeling or cracked bark over necrotic areas.
• Dieback of twigs and smaller branches.
• Premature leaf yellowing and wilting.

The most critical management strategy is the prompt removal of infected branches. Cuts must be made well below the visible canker into healthy wood to ensure all fungal threads are removed.

All pruning tools must be disinfected with alcohol or a bleach solution between cuts to prevent the mechanical transmission of the pathogen to healthy parts of the tree.

Improving tree health through proper irrigation, mulching, and balanced fertilization is essential to boost the tree's natural defense mechanisms against the fungus.

Copper-based fungicides can be applied as a preventive spray in early spring or late autumn to protect vulnerable bark areas and reduce the overall spore load.

Minimize mechanical damage to the trunk and roots during landscaping or maintenance operations, as fresh wounds are the primary entry points for Cytospora platani.